1、A Guide to theAutomationBody of Knowledge2nd EditionA Guide to theAutomationBody of Knowledge2nd EditionVernon L. Trevathan, EditorNoticeThe information presented in this publication is for the general education of the reader. Because neither the author nor the publisher have any control over the us
2、e of the information by the reader, both the author and the publisher disclaim any and all liability of any kind arising out of such use. The reader is expected to exercise sound professional judgment in using any of the information presented in a particular application.Additionally, neither the aut
3、hor nor the publisher have investigated or considered the affect of any patents on the ability of the reader to use any of the information in a particular application. The reader is responsible for reviewing any possible patents that may affect any particular use of the information presented.Any ref
4、erences to commercial products in the work are cited as examples only. Neither the author nor the pub-lisher endorse any referenced commercial product. Any trademarks or tradenames referenced belong to the respective owner of the mark or name. Neither the author nor the publisher make any representa
5、tion regarding the availability of any referenced commercial product at any time. The manufacturers instructions on use of any commercial product must be followed at all times, even if in conflict with the information in this publication.Copyright 2006 by ISAThe Instrumentation, Systems, and Automat
6、ion Society67 Alexander DriveP.O. Box 12277Research Triangle Park, NC 27709All rights reserved.Printed in the United States of America.10 9 8 7 6 5 4 3 2 ISBN 1-55617-984-7ISBN 978-1-55617-984-6No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any
7、 means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publisher.Library of Congress Cataloging-in-Publication Data in ProcessvTable of ContentsPreface, xvBasic Continuous Control, 11 Process Instrumentation, 31.1 Introduction, 31.2 Pressure
8、, 41.3 Level, 51.4 Flow, 81.5 Temperature, 141.6 Smart Instruments, 161.7 References, 17About the Author, 172 Analytical Instrumentation, 192.1 Introduction, 192.2 Sample Point Selection, 202.3 Instrument Selection, 212.4 Sample Conditioning Systems, 212.5 Process Analytical System Installation, 222
9、.6 Maintenance, 242.7 Utilization of Results, 272.8 References, 28About the Author, 283 Continuous Control, 293.1 Introduction, 293.2 Process Characteristics, 313.3 Feedback Control, 313.4 Controller Tuning, 363.5 Advanced Regulatory Control, 413.6 References, 48About the Author, 484 Control Valves,
10、 494.1 Introduction, 494.2 Valve Types, 494.3 Standards and Codes, 524.4 Valve Selection, 534.5 Operation, 554.6 Actuators and Accessories, 564.7 References, 58About the Author, 595 Analog Communications, 615.1 Introduction, 615.2 Pneumatic Signals, 62vi Table of Contents5.3 Current Signals, 635.4 S
11、uppression and Elevation of Zero, 655.5 Other Signals, 665.6 Analog-to-Digital and Digital-to-Analog Conversion, 665.7 References, 73About the Authors, 736 Control System Documentation, 756.1 Reasons for Documentation, 756.2 Types of Documentation, 766.3 Process Flow Diagram (PFD), 776.4 Piping and
12、Instrument Diagrams (P the topics on Digital Communications, Indus-trial Networks and Maintenance have had minor changes; and topics have been added on Continuous Emissions Monitoring Systems and on Custom Software to give more weight to those topics.In addition, an appendix has been added on Contro
13、l Equipment Structure. This appendix goes into some historical detail since an understanding of that history is useful to an understanding of how automation systems are structured today. Prior to the 1970s when programmable control hardware for discrete applications began to see wide-spread use, dis
14、crete control was much more difficult and was thus limited in functionality. However, available analog controllers were very capable for continuous control; so most of the more complex control application work and most of the automation professionals worked on process applications.Today, virtually a
15、ll new control is performed in programmable devices which do a very good job for both discrete and continuous applications. However, the tremendous opportunities in manufacturing (discrete and motion) applications have caused this area to overtake the continuous applications and a major fraction of
16、automation professionals today work outside the process industries.Though a variety of control devices today can do a variety of discrete, motion, and process applica-tions, many of the devices are best suited to specific areas. The design of these devices is influenced by the historical expectation
17、s of that manufacturing area as well as by the true requirements of the auto-mation task.April, 2006Preface to the First EditionThis book is intended to be read and studied both by automation professionals and by those who want to learn about automationnot just used for looking up facts and figures.
18、 However, it contains so much technical information you may also find it useful as a reference. xvi PrefaceBecause each topic was written by a highly respected expert, or experts, in that subject area, there is much more detailed information than you would expect in a typical overview. Even so, each
19、 topic is short enough to be read like a summary.This book emerged from the work to develop ISAs Certified Automation Professional (CAP) program. However, its value is much broader than just as a helpful text for CAP. The topics in this book represent THE scope of automation application, which makes
20、 it one of the most important books published by ISA. This is a unique book that will go a long way toward defining the scope of automation and helping to establish automation “engineering” as a profession.The term “automation” includes all topics that have traditionally been identified using names
21、such as instrumentation, instruments and control, process control, process automation, control systems, automation and control, manufacturing control, manufacturing automation, and system integration. Automation professionals are the practitioners responsible for the direction, design, and deploymen
22、t of systems and equipment for manufacturing and control systems. A number of organizations in recent years have developed a document that defines their knowledge base, frequently referred to as the Body of Knowledge. Some of those documents are bibliographies of the relevant literature, some are a
23、critique of the literature, and some are an overview of the topics. This book is obviously the latter type. Because this book contains only a small fraction of all the infor-mation in automation knowledge, it might be titled “Overview,” “Summary,” or “Introduction.” How-ever, following the lead of t
24、he Project Management Institute with their A Guide to Project Management Body of Knowledge, which is now an ANSI standard, many organizations use the Guide to . . . nomencla-ture. We also have chosen to follow that usage.This book is intended to serve as a technical summary of automation knowledge f
25、or those who need a comprehensive perspective on automation in their job, including: Automation professionals who need to understand the basics of an unfamiliar topic. They might, for example, need to determine if it is useful in the application on which they are currently working. Or, they may have
26、 been assigned to use that technology, and they need to begin to learn about it.Anyone who knows something about a topic, but needs to gain a better understanding of the range of information in the topicAcademicians who need guidance in developing and improving curriculum or courses, and who wish to
27、 expand their own knowledge and that of their studentsManagers who need a better perspective of all aspects of automation, enabling them to bet-ter set direction and make staffing decisionsThose who work in fields related to automation, and who need a comprehensive under-standing of what automation
28、is all about. For example, just as automation professionals need to learn much more about information technology (IT), people in IT working on sys-tems related to manufacturing need to learn more about plant floor control and information systems.Students, novices, and others evaluating career decisi
29、ons Those studying for ISAs Certified Automation Professional (CAP) examTo be useful in all these ways, each of the 35 topics in the book needed to be understandable to those who know very little about that topic while, at the same time, useful to those knowledgeable and experienced in that subject.
30、 And, each topic needed to include real technical informationnot just a Preface xviinewsy overview. Achieving all that was a real challenge in the short space that could be devoted to each topic.Some users will find the material fully meets their educational or reference needs on a particular topic;
31、 others, who find they need more depth or more background, will find it useful to study some of the listed references. Those studying for the CAP exam, for example, may find that this material meets their needs in topics where they have some familiarity, but in topics where they know very little, th
32、ey may also need to consult other sources to adequately understand the material. Also, while this book attempts to cover all the topics in the scope of the CAP exam, many CAP exam questions will not be covered in this book, because CAP questions can be drawn from any book or referred paper in automa
33、tion. Still, a good knowledge of the material in this book will be a big step towards preparing for the CAP exam.The organization of the 35 topics in this book is somewhat arbitrary and evolved from more than a year of work trying to capture as many topics as possible in a logical category. The cont
34、inuous num-bering of the topics from 1 to 35 is to indicate the topics themselves are really the most important headings. The seven topic categories are for convenience only.Deciding what not to include was as big a challenge as deciding what should be covered. Older tech-nologies less used today ha
35、ve been skipped, as well as technologies that are very specialized. Tech-niques used less frequentlyeven ones very important in some applications are often not covered simply because of space limitations. Applications used only by a particular industry are also not included. For example, automation
36、professionals working in chemical and refining applications may feel that distillation column control is so basic that it should have been included. However, those out-side those industriesa majority of todays automation professionalsmay hardly know, or care, what a distillation column is.You may fe
37、el your area of automation is slighted, or find that some topics you consider important in the scope of automation are not addressed. We welcome hearing from you about topics that you think should be included in future editions. If there are errors or topics that need further clarification, please l
38、et us know. Send your comments to infoisa.org. The idea for this book first came from Ken Baker, who, as a member of the CAP Steering Team, real-ized the value of putting the entire scope of automation together into one book. Chip Lee, Director of Publications on the ISA staff, was also a strong pro
39、ponent from the beginning and continued to pursue the idea even though some, including me, initially thought a useful coverage of such a broad scope in one reasonably sized book was not practical. Lois Ferson on the ISA publications staff undertook the big task of identifying authors for each topic
40、and convincing them to deliver a comprehensive technical document in fewer words than they proba-bly imagined possible. Jim Strothman did the editing for format and style and to overcome our ten-dency as engineers to use too many unnecessary words. But it is the authors of the 35 topics who are most
41、 responsible for this book. Though many of them initially resisted the tough assignment of cover-ing significant technical detail in such a small space, particularly with a tight time schedule, each did an outstanding job addressing their topic. Many of the authors have written books specifically on
42、 their topic, and a number of the authors are the recognized expert on their topic. About a third of the authors are ISA Fellows.Vernon TrevathanSeptember, 20051Basic Continuous ControlSome might call this category “process control” or “instrumentation and control,” because the material in these top
43、ics is closest to the historical scope of ISA and is consistent with ISAs original name, Instrument Society of America. But today, proportional, integral, derivative (PID) and other continuous control techniques are used in many applications outside the process industries. For example, they are used
44、 in areas such as automotive paint shop controls, motion controls, electrical equipment controls, building automation, ship stabilization controls, and many, many other areas. PID is so pervasive that one could not be considered well educated as an automation professional if he or she does not know
45、the basic concepts of PID and PID tuning. In fact, the CAP Steering Team decided early on that, while many people today work with manufacturing automation information technology that does not involve basic plant floor control, it did not make sense for them to be called automation profes-sionals wit
46、hout knowing the basics of plant floor controlincluding continuous control.Measurements are extremely important in any automation task. It is really true you can control well only those things that you can measureand accuracy and reliability requirements are continuing to increase. Continuous instru
47、mentation is required in many applications throughout automation, although here we call it process instrumentation because the particular type of transmitter packaging discussed is more widely used in process applications. There are so many measurement principles and variations on those principles t
48、hat this topic can only scratch the surface of all the available ones, but it hopefully covers the more popular types. Analytical Instrumentation and Control Valves are more applicable to process applications, although these also are used in environmental and other applications in a variety of indus
49、tries. The type of control system documentation discussed here is also more specific to process industries, but many outside processes can learn from the high degree of development of these documentation conventions. The control equip-ment topic in this category covers what has traditionally been called distributed control systems (DCSs), although that designation no longer has intrinsic meaning. Control valves are critical components of a control loop in process and utility industries. It has often been demonstrated that, in nearly all process plants, control valve problems a
